1. Field of the Invention
The present invention relates to a sheet stacking device for stacking sheets, an image forming apparatus, such as a copying machine, a printer or a facsimile, and an image forming apparatus having a plurality of functions of the functions of the copying machine, the printer and the facsimile.
2. Description of Related Art
In conventional image forming apparatuses, such as a copying machine, a printer, a facsimile, etc., it is general that a sheet discharge tray onto which a sheet having an image formed thereon is discharged, an original stacking tray and original discharge tray for an original, etc., are disposed on the side portion or portions of a frame body of the image forming apparatus. However, in recednt years, for the purpose of reducing a space required for installation of the image forming apparatus, it has been proposed that the sheet discharge tray, the original stacking tray and the original discharge tray are disposed on the upper portion of the image forming apparatus.
Further, in recent years, in image forming apparatuses of the kind having both an image forming part for forming an image on a sheet and an original reading part for reading image information from an original, there is widespread a composite apparatus, called MFP (Multi-Function Peripheral), having a plurality of functions including the functions of a copying machine, a facsimile, a printer, etc.
Such an MFP is required to be provided with a plurality of sheet discharge ports and a plurality of sheet stacking trays and to have a selective stacking (sorting) function of selectively stacking sheets on the applicable trays by switching the use of the sheet discharge port from one port over to another according to the purpose of the copying machine, the facsimile or the printer, and is required, from the viewpoint of an improvement in operability, to enable all the basic operations to be performed from the front side of the MFP.
An example of an image forming apparatus arranged as such an MFP is described with reference to FIG. 5.
FIG. 5 is a schematic sectional view showing a facsimile apparatus arranged as an MFP. Referring to FIG. 5, the facsimile apparatus has a frame body part 1, an original reading part 2 for reading image information from an original D, an image forming part 3 composed of a laser beam printer of an electrophotographic system, an original loading tray 4 arranged to allow a plurality of sheets of original D to be loaded thereon, a slider 18 arranged to be movable in the direction of width of the original D for regulating the width of the original D loaded on the original loading tray 4, and an original discharge tray 5 arranged to allow the original D to be stacked thereon when the original D is discharged after the image information of the original D is read by the original reading part 2.
In the facsimile apparatus, an arrow A indicates the direction of the front side of the frame body part 1, i.e., a frontward direction of the apparatus. The user of the apparatus sets, from the frontward direction of the apparatus, the original D on the original loading tray 4 in the direction of an arrow B, and then operates an operation part composed of operation buttons, etc., (not shown). When the original D is discharged from the original reading part 2 onto the original discharge tray 5, the user takes out the original D in the direction of an arrow C.
Further, the facsimile apparatus is further provided with a sheet discharge tray 6 onto which a sheet having an image formed thereon by the image forming part 3 is discharged and stacked. The sheet having an image formed thereon passes through a sheet discharge route R1 to be discharged onto the sheet discharge tray 6. The sheet as discharged is taken out in the direction of an arrow E by the user, as in the case of the original D, stretching his or her hand from the frontward direction of the apparatus. The conventional facsimile apparatus of this kind is thus arranged to allow the user to perform all the basic operations from the front side of the frame body part 1, i.e., from the frontward direction of the apparatus.
However, in such a conventional image forming apparatus, in inserting the original D, in taking out the original D and in taking out the sheet, the user must perform an operation while standing on the front side of the apparatus in the frontward direction of the apparatus, and look at the individual trays and the sheet of the original or the image-formed sheet on the respective trays from the direction of an arrow J (called a visual line J) as shown in FIG. 5.
However, the original loading tray, the original discharge tray and the sheet discharge tray, which are trays having respective different functions, are located close to each other. In addition, the user must perform an operation in a posture of looking downward at forefront portions of the respective trays, as indicated by an arrow H in FIG. 5. Therefore, the following problem arises.
To carry out the above-stated function of sorting a sheet for one purpose from a sheet for another purpose, it is necessary to provide an additional sheet discharge tray (hereinafter referred to as an upper sheet discharge tray) between the sheet discharge tray 6 and the original discharge tray 5. With the upper sheet discharge tray thus provided, the total height of the apparatus increases. In order to suppress the increase in total height of the apparatus, the spacing distances between the respective trays must be arranged to be shorter.
However, with the spacing distances between the respective trays shortened, it becomes difficult for the user to discern the original loading tray 4, the original discharge tray 5 and the sheet discharge tray 6. Such an arrangement, therefore, tends to cause erroneous operations on the trays.
In particular, in recent years, in a composite apparatus having the copying function and the printer function in addition to the facsimile function, there has been such a proposal that, in providing the above-mentioned sorting function, in order to prevent sheets discharged in different modes, such as the copying mode, the facsimile mode and the printer mode, from mixing together, a sheet discharge tray onto which a sheet is discharged in a respective one of the different modes can be set beforehand selectable.
However, even in the case of this proposal, if the trays are spaced closer for suppressing the total height of the apparatus, it is still difficult to discriminate a tray onto which the sheet of an applicable mode is discharged from the other trays, so that an erroneous operation tends to take place.
Further, in the case of the facsimile apparatus shown in FIG. 5, the fore end parts of the respective trays are located approximately on one and the same plane. Therefore, when the user views the trays from the position of the visual line J, the trays are hidden by the uppermost tray, necessitating the user to grope for the applicable tray. Such groping tends to cause a mistake of the operation. To avoid such mistaking, when inserting or taking out a sheet into or from the applicable tray, the user has to view the position of each tray while stooping down to change the visual line J to the direction of the arrow H (hereinafter referred to as the visual line H). The operability of the apparatus, therefore, has been inadequate.
Further, when taking out a sheet or sheets from each of the trays, the user grasps the fore end of the sheet. However, if the fore end part of another tray located just above the applicable tray is located just above the fore end of the sheet to be taken out, the sheet cannot be easily taken out because the upper tray becomes an obstruction.
Further, in the case of a facsimile or a printer, a sheet taken out once from a tray is sometimes put back to the tray. In such a case, if the tray is hidden by another tray located just above the tray, the operation of putting the sheet back to the applicable tray is not easy, thereby degrading the operability of the apparatus.
The problem described above may be solved by increasing the vertical spacing distance between the trays to make the user""s hand readily insertable. However, such a solution not only causes an increase in the height of an operation plane of each tray part but also causes the increase in size of the apparatus, resulting in an increase in cost.
It is an object of the invention to provide an image forming apparatus arranged to have excellent operability in respect of observability of trays, taking and inserting sheets out of and onto the trays, etc., without increasing the height of the apparatus.
It is another object of the invention to provide an image forming apparatus arranged such that an operation means thereof has excellent observability and operability when the user of the apparatus performs a setting operation on the operation means while standing at the position in front of a frame body part of the apparatus, i.e., at the position on the front side of the apparatus.
To attain the above objects, in accordance with an aspect of the invention, there is provided a sheet stacking device, comprising a plurality of sheet trays for stacking sheets thereon, the plurality of sheet trays being disposed to be piled substantially in a vertical direction, wherein an end part in a width direction of at least one sheet tray of the plurality of sheet trays is shifted, in the width direction of the at least one sheet tray, from an end part in a width direction of another sheet tray of the plurality of sheet trays.
Further, in accordance with another aspect of the invention, there is provided an image forming apparatus, comprising image forming means for forming an image on a sheet, a frame body having the image forming means, original reading means disposed above the frame body for reading image information from an original, an original loading tray arranged to load thereon the original from which the image information is to be read by the original reading means, an original discharge tray piled with the original loading tray and arranged to discharge thereonto the original from which the image information has been read by the original reading means, and a sheet discharge tray disposed above the frame body and below the original discharge tray to be piled with the original discharge tray, and arranged to discharge thereonto the sheet on which the image has been formed by the image forming means, wherein end parts in a width direction of the original loading tray and the original discharge tray are located substantially at the same positions on both sides in the width direction, and an end part in a width direction of the sheet discharge tray is shifted, in the width direction of the sheet discharge tray, from the end parts in the width direction of the original loading tray and the original discharge tray.
These and other objects and features of the invention will become apparent from the following detailed description of a preferred embodiment thereof taken in connection with the accompanying drawings.